import { stat } from "node:fs/promises";
import { dirname, join } from "node:path";
import { spawnCli } from "@uncaged/workflow-util-agent";
import type { AdapterFn, RoleResult, ThreadContext, WorkflowRuntime } from "@uncaged/workflow-runtime";
import * as z from "zod/v4";

export type DifferAdapterConfig = {
  command: string | null;
  timeout: number | null;
};

type SpawnCliFn = typeof spawnCli;

export function createDifferAdapter(
  config: DifferAdapterConfig,
  spawnCliFn: SpawnCliFn = spawnCli,
): AdapterFn {
  const command = config.command ?? "docx-diff";
  return <T>(_systemPrompt: string, schema: z.ZodType<T>) =>
    async (ctx: ThreadContext, _runtime: WorkflowRuntime): Promise<RoleResult<T>> => {
      const officeStep = ctx.steps.find((s) => s.role === "office");
      if (officeStep === undefined) {
        throw new Error("differ: office step not found in ctx.steps (invariant violation)");
      }

      const officeMeta = officeStep.meta as { outputDocx: string; sourceDocx: string };

      const { outputDocx, sourceDocx } = officeMeta;
      const reportPath = join(dirname(outputDocx), "diff_report.html");

      const result = await spawnCliFn(
        command,
        [sourceDocx, outputDocx, "-o", "html", "--out-file", reportPath],
        { cwd: null, timeoutMs: config.timeout },
      );

      if (!result.ok) {
        const e = result.error;
        if (e.kind === "non_zero_exit" && e.exitCode === 1) {
          // docx-diff exits 1 when documents have differences — this is a success path
        } else if (e.kind === "non_zero_exit") {
          throw new Error(`differ: docx-diff failed (exit ${e.exitCode}): ${e.stderr}`);
        } else if (e.kind === "timeout") {
          throw new Error("differ: timed out");
        } else {
          throw new Error(`differ: spawn failed: ${(e as { message: string }).message}`);
        }
      }

      try {
        await stat(reportPath);
      } catch {
        throw new Error(`differ: report file not found: ${reportPath}`);
      }

      const meta = schema.parse({ outputDocx, sourceDocx, diffReport: reportPath });
      return { meta, childThread: null };
    };
}